consider using-fields only if left type has no monomorphs, and then also check constraints (fixed issue #1466)

git-svn-id: http://haxe.googlecode.com/svn/trunk@6181 f16182fa-f095-11de-8f43-4547254af6c6
added DateTools.makeUtc

git-svn-id: http://haxe.googlecode.com/svn/trunk@6182 f16182fa-f095-11de-8f43-4547254af6c6
[Php] Array.filter fix (fixed issue #1477)

git-svn-id: http://haxe.googlecode.com/svn/trunk@6183 f16182fa-f095-11de-8f43-4547254af6c6
give proper error on rare unify_min case

git-svn-id: http://haxe.googlecode.com/svn/trunk@6184 f16182fa-f095-11de-8f43-4547254af6c6
Some work on extern generation

git-svn-id: http://haxe.googlecode.com/svn/trunk@6185 f16182fa-f095-11de-8f43-4547254af6c6